Calculating Forces and Efficiency of a Pressure Washer

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In summary, the conversation discusses a question regarding a pressure washer and its power, efficiency, nozzle diameter, and reaction force. The attempt thus far includes using equations to calculate the power and efficiency, finding the cross sectional area of the nozzle, and using linear momentum to calculate the reaction force. Further assistance is needed to complete the final part of the question.
  • #1
Cret
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I'm having trouble with this question. Any guidance would be very welcome. I have left the values out because i want to do the maths myself.

Data
Pressure washer delivers xxx litres per hour of water
Pressure xx bar
Draws xxxx Watts of power

Question
a.) Show power in water flow is xxx watts
b.) Calculate efficiency between electrical input energy to hydraulic energy in water
c.) Calculate diameter of output nozzle of the washer
d.) Use the cross sectional area of the nozzle to calculate the reaction force exerted on the user

Attempt thus far:

P = Power (Watts)
p = Pressure (N/mm2)
Q = Flow rate m3/s
n = Efficiency
v = velocity (m/s)
A = Area
Vjet = velocity of jet
g = 9.81

For a.) I used

P = p x Q
Converting xxx litres per hour to litres per second and xx bar to N/mm2

For b.) I used

n = output / input = answer x 100%

For c.)

Initially I found the velocity of the output jet in meters per second

Vjet = sq root 2 x g x p = m/s

Then I rearranged

Q = v x A
A = Q/v

Which gave me the cross sectional area of the nozzle

For d.) I’m have a little trouble with the final part
 
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  • #2
The reaction force is the force required to hold the power washer nozzle steady. Use Linear momentum, F= ma=mass flow rate X Velocity. You know Q in l/hr, the density of water and velocity of the water.
 
  • #3
Many thanks this helped at lot!
 

What is a pressure washer?

A pressure washer is a mechanical device that uses high-pressure water to remove dirt, grime, and other debris from surfaces such as buildings, vehicles, and outdoor spaces.

How does a pressure washer work?

A pressure washer has a motor or engine that powers a pump, which pressurizes the water from a connected hose. The high-pressure water is then released through a nozzle at the end of a wand, allowing for targeted cleaning and removal of dirt and grime.

What are the benefits of using a pressure washer?

Pressure washers offer a quick and efficient way to clean surfaces, as the high-pressure water can remove stubborn dirt and grime in a fraction of the time it would take to scrub by hand. They are also environmentally friendly, as they use less water than traditional cleaning methods.

What surfaces can be cleaned with a pressure washer?

Pressure washers can be used on a variety of surfaces, including concrete, brick, vinyl, wood, and metal. However, it is important to select the appropriate pressure and nozzle for each surface to avoid causing damage.

Are pressure washers safe to use?

When used properly, pressure washers are generally safe to use. However, caution should be taken when operating the machine, as the high-pressure water can cause injury. It is important to wear protective gear and follow the manufacturer's instructions for safe and effective use.

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